Temperature sensor circuits measure the temperature of electrical devices. Some electrical devices include a dedicated temperature sensor circuit that measures the temperature of the electrical device. The temperature sensor circuit provides crucial information regarding the operation of an electrical device to avoid overheating.
Typically, temperature sensor circuits include a voltage supply (Vcc) connected to a resistor (R) or constant current source (CCS) as shown in FIG. 1. The resistor is connected to a transistor (Q). The transistor is in a vicinity or close proximity to a device 102, where the device receives heat from the transistor. Typically, the device is a fan, transistor, control module etc. A base and collector of the transistor Q and the resistor or CCS are connected to a signal conditioner 101. Typically signal conditioner 101 comprises components such as amplifiers, resistors, and microprocessors. When Vcc is activated, a collector current (Ic) at transistor Q, a collector to emitter voltage (Vce) at transistor Q and a base to emitter voltage (Vbe) at transistor Q are produced. If the transistor is saturated, then Vbe temperature coefficient is more stable as the collector current varies. This functionality is graphically illustrated in FIG. 2, where the Vbe temperature coefficient of transistor Q as a function of collector current Ic is shown.
This nonlinear relationship of Ic and the Vbe temperature coefficient makes it burdensome to accurately assess the temperature at the device being monitored. In addition, this temperature sensor circuit is a separate circuit that requires many components and extra space on a circuit board.
Accordingly, there is a need for an apparatus and a method to measure a temperature of the electrical device that provides a simple and accurate assessment of the temperature of the device at minimal cost and complexity.